In a wireless local area network (WLAN) system, when a plurality of stations (STAs) 111 and 112 located in a same basic service set (BSS) perform data transmission with respect to an access point (AP) 100 simultaneously, air-time collision inevitably occurs due to characteristics of a channel access scheme in view of collision avoidance, which is a hidden node problem.
In addition, when STAs located in different adjacent BSSs perform data transmission, interference may also be generated, thereby reducing efficiency of data transmission originally desired.
To relieve such problems, opportunities to access STAs may be temporally distributed for each BSS to avoid collision on frequency resources. However, the foregoing expected object may also be achieved by spatially distributing channel access attempts using an AP including a sector antenna. Such a technology is called sectorization.
In general, the sector antenna includes a plurality of planar antennas and may have a function of selectively switching transmission antennas and reception antennas. A device functioning as the sector antenna may be implemented using a combination of multiple antennas and signal processing such as beam forming. The sectorization has neither been used in the conventional WLAN nor technically discussed, due to an operational inconvenience.
However, in a recent WLAN standard considering a sensor application, indoor/outdoor M2M, and extended range cellular offloading as a main application, coverage is increased up to approximately 1 kilometer (km). Furthermore, since a number of STAs managed by a single BSS is increased up to several thousands to several tens of thousands, effective data transmission is unable to be performed due to the hidden node problem and an overlapping basic service set (OBSS) interference problem. Accordingly, there is a desire for technology that may reduce such issues by spatially dividing operations of STAs through sectorization in the WLAN system.